Mutation and Evolutionary Rates in Adélie Penguins from the Antarctic

Abstract

Precise estimations of molecular rates are fundamental to our understanding of the processes of evolution. In principle, mutation and evolutionary rates for neutral regions of the same species are expected to be equal. However, a number of recent studies have shown that mutation rates estimated from pedigree material are much faster than evolutionary rates measured over longer time periods. To resolve this apparent contradiction, we have examined the hypervariable region (HVR I) of the mitochondrial genome using families of Adélie penguins (Pygoscelis adeliae) from the Antarctic. We sequenced 344 bps of the HVR I from penguins comprising 508 families with 915 chicks, together with both their parents. All of the 62 germline heteroplasmies that we detected in mothers were also detected in their offspring, consistent with maternal inheritance. These data give an estimated mutation rate (μ) of 0.55 mutations/site/Myrs (HPD 95% confidence interval of 0.29–0.88 mutations/site/Myrs) after accounting for the persistence of these heteroplasmies and the sensitivity of current detection methods. In comparison, the rate of evolution (k) of the same HVR I region, determined using DNA sequences from 162 known age sub-fossil bones spanning a 37,000-year period, was 0.86 substitutions/site/Myrs (HPD 95% confidence interval of 0.53 and 1.17). Importantly, the latter rate is not statistically different from our estimate of the mutation rate. These results are in contrast to the view that molecular rates are time dependent.

Inverse relationship between genetic diversity and epigenetic complexity

“…If the real phenomenon here is non-equidistance with equidistance being coincidental, one would expect to see much larger variations in distance. Thus, the data shows that the real phenomenon here is equidistance [4].…”

“…The genetic equidistance result is extremely robust and universal and has been independently confirmed for numerous proteins and numerous species [4]. It is the most remarkable result of molecular evolution since it was completely unexpected from classical Neo-Darwinian theory.…”

“…Actual mutation rate in real time is faster than that calculated from phylogenetic analysis. It is well known that mutation rate from pedigree analysis on genealogical timescales is often an order of magnitude or more greater than mutation rate from phylogenetic analysis over geological time [3,4]. Thus, phylogenetic diversity or distance over geological time is uncoupled from actual mutation rate observed on genealogical timescales.…”

“…Importantly, few recognized that results of violations of a constant molecular clock do not invalidate the genetic equidistance result [4]. The equidistance result does not necessarily mean rate constancy.…”

“…The MGD hypothesis predicts that simple organisms should show higher genetic diversity than complex organisms after the same amount of time of evolution. Indeed, flowering plants have much greater genetic diversity than mammals even though they have both coevolved for similar amount of time [4]. Flowering plants are less complex in epigenetic programs and have zero PRDM family of epigenetic enzymes while mammals have 16 to 17.…”